WordPress at a glance
function is not described

Composer\Autoload

ClassLoader::loadClass() public WC 1.0

Loads the given class or interface.

{} It's a method of the class: ClassLoader{}

No Hooks.

Return

true|false|null. True if loaded, null otherwise

Usage

$ClassLoader = new ClassLoader();
$ClassLoader->loadClass( $class );
$class(string) (required)
The name of the class

Code of ClassLoader::loadClass() WC 5.3.0

<?php
public function loadClass($class)
{
    if ($file = $this->findFile($class)) {
        includeFile($file);

        return true;
    }
}